The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As is known in itself, an aircraft engine nacelle makes it possible to channel the outside air toward that engine, and to ensure the discharge of that air at a high speed so as to supply the necessary thrust.
In dual-flow turbojet engines, the flow of air mixed by the fan is divided, downstream thereof, into a primary flow (also called “hot”) that enters the core of the turbojet engine to undergo several compressions and an expansion therein, and the secondary flow (also called “cold”), which circulates inside a substantially annular tunnel, defined on the one hand by an engine fairing (the internal fixed structure, also called “IFS”), and on the other hand by the thickness of the nacelle.
The flow of cold air, which exits downstream of the nacelle through an exhaust nozzle defined by the downstream edge of that nacelle, provides the majority of the thrust.
For aerodynamic optimization reasons, and thus fuel optimization reasons, it is completely advantageous to be able to adjust the section of the cold air flow discharge downstream of the nacelle: it is in fact useful to be able to increase that section during the takeoff and landing phases, and to reduce it during cruising phases: the term Variable Fan Nozzle (VFN) is often used.
It should be noted that this variable-geometry nozzle may be a single piece, or may be made up of two halves, or may be formed by juxtaposing deflector flaps: in the context of this document, the term “variable-geometry nozzle” will cover all possible scenarios.
Furthermore, as is known in itself, the nacelle very frequently incorporates thrust reversal means, which can move between a cruising position, also called “direct jet”, and a thrust reversal position, also called “reverse jet,” making it possible to orient part of the secondary flow of air in the upstream direction of the nacelle during landing, which actively contributes to the braking of the aircraft.
These thrust reversal means are often of the cascade vane type, i.e. they include a series of vanes arranged downstream of the fan case, on the periphery of the cold flow tunnel, said vanes being able to be uncovered on command by a thrust reverser cowling slidingly mounted on the structure of the nacelle.
The variable-geometry nozzle is situated in the downstream extension of the thrust reverser cowling, and it is important to be able to actuate these two parts of the nacelle independently: it is in particular desirable to be able to increase the cross-section of the variable-geometry nozzle without actuating the thrust reverser means, in particular during takeoff.
To perform this independent actuation, the prior art teaches the solution consisting of using dual-rod jacks (also called “telescoping”), one rod actuating the thrust reverser cowling, and the other rod actuating the variable-geometry nozzle.
Such jacks are heavy, and are also not suitable for the specific case of variable-geometry nozzles made up of pivoting deflector flaps: the pivoting of those flaps in fact tends to cause a misalignment of the rods of the jacks.